Process of making mortised printing plates



May 13, 1952 H. OETTINGER, JR 2,596,715

PRQCESS OF MAKING MORTISED PRINTING PLATES Filed Feb. 19, 1947 g2 PRESSURE I I 15 HAMMER W INVENT HENRY OETTINGE R.

ATTORNEYS Patented May 13, 1952 PROCESS OF MAKING MORTISED PRINTING PLATE S Henry Oettinger, Jr., Forest Hills, N. Y., assignor to Electrographic Corporation, New York, N. Y., a corporation of Delaware Application February 19, 1947, Serial No. 729,605

3 Claims. 1

The present invention relates to a new and useful process of making mortised plastic printing plates.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the processes, steps and combinations pointed out in the appended claims.

The invention consists in the novel steps, processes, combinations and improvements herein shown and described.

The accompanying drawings, referred to herein and constituting a part hereof, illustrate a preferred manner of apparatus in accordance with this invention for carrying out the process of the invention, and together with the description, serve to explain the principles of the invention.

Of the drawings:

Figure 1 is a schematic sectional view showing a first step in the process of the present invention;

Figure 2 is aperspective view, partially broken away, of a temporary insert used in the present process;

Figure 3 is a fragmentary, schematic sectional view of a printing plate matrix used in the process and resulting from the step shown in Figure 1;

Figure 4 is a schematic sectional view showing the formation of a plastic printing plate from the matrix of Figure 3;

Figure 5 is a fragmentary sectional view show ing schematically the removal of the insert and the formation of the mortise; and

Figure 6 is a perspective, sectional view showing a modified form of insert for use in a modification of the process of the present invention.

Printing plates are often provided with rectangular openings or mortises for receiving changeable type matter; for example, a national advertiser often sends such plates to different publications, the plate serving for the main portion of the advertisement, while the mortise allows the price, local dealer's name or other changeable matter to be inserted just prior to the time of printing. Usually such plates are routed out, filed or otherwise cut to form the mortise, but this requires considerable time and often the mortise is not accurately formed nor uniformly positioned in the plate, and when'the printing plates are of plastic material, the difficulty and expense are greater than with metal printing plates.

The present invention has for its object the provision of a novel and improved process for the rapid and economical production of plastic printing plates having accurately formed mortises. A further object is the provision of an improved process by which mortised printing plates of plastic material, such as hard vinyl resin may be produced with substantially the same operations as have been required for the production of unmortised plates of similar material.

In accordance with the present invention, the original printing plate (for letterpress printing) which is to be duplicated as a plastic printing plate is provided with a mortise," which is a rectangular opening, located as desired. Into this mortise is fitted a rectangular block of metal or other suitable material which substantially fills the opening and is of a thickness to be slightly less than the thickness of the printing plate to be formed. This block or temporary insert may be formed of steel, other relatively hard metal, or any other hard substance that does not bond with the synthetic resins used. On the interface between the mold and original plate, the block is provided with locating means by which the block may be accurately located on the mold, or may be permanently secured thereto. When properly located, the block is slightly below the face of the original printing plate and, is spaced from the back face of the original by a thin sheet of lead or other softer material which is separable from the block.

In this condition, a sheet of laminated fibrous material, such as heavy three ply paper impregnated with an induratable synthetic resin, such as a phenol-formaldehyde resinous condensation product, as is commonly used for the production of molds, is placed over the printing plate original, both are inserted between heated platens and the laminated mold material is pressed into the face of the original and held under pressure while it is heated until the resin has been set. When set, the two are removed from the press. and the mold is separated from the original and trimmed to the desired size, the block remaining with the mold as a surface projection thereon.

The matrix is then placed on a flat sheet of metal with its indented face upward. The indentations of the face are preferably filled with fine plastic granules or powder, after which the face of the mold is covered with a layer of coarser plastic particles, to a depth sufficient so that the finished plate will be of the desired thickness. For convenience, during this operation, the mold is usually surrounded by flat thick bars which serve as levelling guides for levelling the powder on the mold and limiting its spread.

The resinous powder is preferably a thermoplastic resin or substantial hardness, good wearing properties and without fibrous filler. such as a vinylchloride-vinylacetate resin (20-30% chloride) of relatively large molecular weight (such as 4000 to 6000), one suitable resin being VG 9400 as manufactured by The Bakelite Corporation. This resin is thermoplastic and may be molded at a temperature of about 250 F. to 300 F. under normally heavy molding pressures.

The layer of resinous powder is sufficiently thick to cover the temporary insert and form a thin sheet over the intended mortise opening. The insert may be permanently held on the mold. or alternatively may be located thereon and form a temporary part of the duplicate plate, in which case, the insert is driven through the plate as the plate is firmly supported over an opening, thereby removing the insert and cleanly breaking the mortise in the plate. If the insert is held on the mold, it is pulled away from the plate as the plate and mold are separated and the thin wall over the mortise opening need only be broken away and filed'or otherwise treated to remove the rough edges.

The duplicate plate may then be trimmed to dimensions and the insert, if of the removable type may again be located on the mold for forming another duplicate plate.

It will be understood that the foregoing general description and the following detailed description as well are exemplary and explanatory of the invention but are not restrictive thereof.

Referring now in detail to the accompanying drawings which illustrate typical steps in the preferred manner of carrying out the process of the present invention, Figure 1 shows the formation of a mold from an original metal printing plate, such as a halftoneor text plate for letterpress printing. In this figure, the original plate I is a metal printing plate having a rectangular mortise opening .12, and is customarily 0.105 thick. Within the mortise opening is a steel insert or block 14 having on its upper face two or more depressions I5 which are preferably drill holes with cylindrical-sides and smooth conical bottoms. The blocks 14 may conveniently be 0.078" thick and are supported by a thin block,

for instance a similarly shaped piece [6 of lead, 0.052" thick, the total of the thicknesses of pieces I4 and 16 being less than that of the plate 10. By providing that the surface of the block I4 is below the surface of the plate [0, the mold to be formed will have bevelled or rounded edges 42 at the margins of the mortise l2 by reason of the poor flow of the laminated mold stock during molding. r

. The block. 14 is preferably covered with powdered thermosetting resin 18 over the depressions which will bond with the laminated mold stock to form locating pins for the block 14.

A sheet of laminated, impregnated thermosetting mold material 20 is then placed over the plate l0, heated and subjected to pressure and continued heat between the platens 22 of a hydraulic press to form-the moldwhich is an accurate replica ofthe plate Hi. There results a mold such as that shown in Figure 3 in which bosses 24 form locating pins for the block [4.

The mold 20 is then inverted and surrounded by margin bars (not shown) and is preferably filled with a fine powder of thermoplastic resin,

such as a vinyl resin preferably VG 9400. Thereafter, the mold 28 is covered by a thick layer 26 of coarser similar resin, suflicient thickness being provided to produce a finished duplicate plate of the desired thickness (commonly 0.105). The resin is then heated, subjected to heavy pressure between the platens of a hydraulic press, as shown in Figure 4 for a sufficient time and at sufficient temperature and pressure to form an accurate thermoplastic duplicate plate 28 from the thermosetting resin mold 20.

When the molding is completed, the plate 28 is separated from the mold 20, insert I 4 staying with the plate and being covered on one side by a thin web of resin 3% over the mortise opening l2. This is highly desirable but not essential and the web 30 results from sufficient thicknesses of resin powder being provided to insure proper flow over the mold.

The molded plate 28 is then placed over a rigid .plate 32 having an aperture 34 therein and a hammer blow on the insert 14, as it is located over aperture 39 serves to punch out the web 30 and usually finishes the plate, except for trimming. Sometimes, however, a slight file finishing of the edges of the mortise opening in the plate 23 may be required,

The insert it is then repositioned on the locating bosses 25 which insure accurate positioning of the insert.

If desired, the insert 14' may be permanently attached to the mount 29, and for this purpose I find it preferable to use the form of insert shown in Figure 6 of the drawings. In this form the insert It is formed with-two holes through which are inserted split rivets 40 having their prongs spread apart so that they may be embedded in and securely retained by the thermosetting resin of the mold 20. After the mold is formed, the exposed surface of the metal pieces 48 is roughened so as to insure its holding a small quantity or plastic 25 over it. After the molding of the plastic plate has been completed, the plate is stripped from the mold and the thin web 30 can be easily broken out and any rough edges finished with a knife or file.

By making the surface of the insert l4 below the surface of the plate 10, the mold has slightly rounded edges 42 at the mortise l2 and this results in similarly rounded edges 44 on the duplicate plate, thereby avoiding the necessity of finishing the duplicate plate at these points.

The invention in its broader aspects is not limited to the specific process and steps shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. The process of forming mortised duplicate plastic printing plates which comprises locating a temporary insert block in the mortise opening of i an original plate, forming a mold from said origmold and block from the plate, covering the mold and block with thermoplastic material, subjecting it to heat and pressure to form a duplicate plastic [plate with the temporary insert in the duplicate plate and forming the mortise opening and removing the temporary insert from the duplicate plate.

2. The process of forming mortised duplicate plastic printing plates which comprises locating a temporary insert block in the mortise opening of an original plate, said block lying wholly below the general surface level of the original plate, forming a mold from said original plate by pressing a sheet of thermosetting impregnated material onto said plate under heat and pressure to form a mold said block being formed with indented portions adjacent the mold by which the block is located on the mold, removing the mold and block from the plate, covering the mold and block with thermoplastic material, subjecting it to heat and pressure to form a duplicate plastic plate with the temporary insert in the duplicate plate and forming the mortise opening and removing the temporary insert from the duplicate plate.

3. The process of forming mortised duplicate plastic printing plates which comprises locating a block corresponding to the mortise on the face of a mold, covering the face ,of the mold and the block with powdered thermoplastic material and subjecting the powder to heat and pressure to form a plate therefrom having a thin web overlying'the mortise opening, and using the block as a punch to remove said web and clear the mortise opening.

HENRY OETTINGER, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 903,189 Holstein Nov. 10, 1908 1,380,919 Maier June 7, 1921 1,401,633 Novotony Dec. 27, 1921 1,636,346 Wood July 19, 1927 1,707,729 Kelly Apr. 2, 1929 2,071,646 Melind Feb. 23, 1937 2,078,535 Hagedorn Apr. 27, 1937 2,084,427 Broderson June 22, 1937 2,087,470 Davidson et a1 July 20, 1937 

